package com.mbatis.juc.rw;

import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;

/**
 *
 * 独占锁 （写锁） 一次只能被一个线程占有
 * 共享锁 （读锁） 多个线程可以同时占有
 * ReadWriteLock
 * 读-读  可以共存
 * 读-写  不能共存
 * 写-写  不能共存
 *
 */

public class ReadWriteLockDemo {

    public static void main(String[] args) {

//        MyCache myCache = new MyCache();
        MyCacheLock myCache = new MyCacheLock();

        // 存入
        for (int i = 1; i <= 5; i++) {
            final int tmp = i;
            new Thread(() -> {
              myCache.put(String.valueOf(tmp),tmp);
            },String.valueOf(i)).start();
        }

        for (int i = 1; i <= 5 ; i++) {
            final int tmp = i;
            new Thread(() -> {
                myCache.get(String.valueOf(tmp));
            },String.valueOf(i)).start();
        }




    }
}


class MyCache{
    private Map<String,Object> map = new HashMap<>();


    public void put(String key,Object value){
        System.out.println(Thread.currentThread().getName()+"写入"+key);
        map.put(key,value);
        System.out.println(Thread.currentThread().getName()+"写入OK");
    }


    public void get(String key){
        System.out.println(Thread.currentThread().getName()+"读取"+key);
        Object o = map.get(key);
        System.out.println(Thread.currentThread().getName()+"读取OK");
    }
}

class MyCacheLock {
    private Map<String,Object> map = new HashMap<>();
    // 读写锁: 更加细粒度的控制
    private ReadWriteLock readWriteLock = new ReentrantReadWriteLock();

    // 存、写入的时候，只希望同时只有一个线程写
    public void put(String key,Object value){
        readWriteLock.writeLock().lock();
        try {
            System.out.println(Thread.currentThread().getName()+"写入"+key);
            map.put(key,value);
            System.out.println(Thread.currentThread().getName()+"写入OK");
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            readWriteLock.writeLock().unlock();
        }
    }

    // 取、读，所有人都可以读
    public void get(String key){
        readWriteLock.readLock().lock();
        try {
            System.out.println(Thread.currentThread().getName()+"读取"+key);
            Object o = map.get(key);
            System.out.println(Thread.currentThread().getName()+"读取OK");
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            readWriteLock.readLock().unlock();
        }
    }
}